The present invention relates to a sliding track assembly for a drawer and, more particularly, to a durable sliding track assembly, which prevents interference of the parts with one another when moving the drawer in or out of a desk, and has means to support the parts in position.
A regular two-step sliding track assembly for a drawer, as shown in FIGS. from 1 through 3, is generally comprised of an inner rail 91, an intermediate rail 92, and an outer rail 93. When pulling the drawer outwards, the inner rail 91 is moved with the drawer out of the intermediate rail 92 at the initial stage as shown in FIG. 2, and then the intermediate rail 92 is pulled out of the outer rail 93 as shown in FIG. 3. Because the inner rail 91 bears the whole weight of the load when pulling the drawer out of the desk, the coupling area between the inner rail 91 and the intermediate rail 92 tends to be damaged.
FIGS. from 4 through 9 show another structure of prior art sliding track assembly. According to this design, the inner rail 94 and the intermediate rail 95 commonly bear the weight of the load at the initial stage when pulling the drawer out of the desk. However, when pulling the inner rail 94 outwards, the pressing force of the stop member 97 against one sidewall 941 of the inner rail 94 tends to be overcome by the pulling force employed to the inner rail 94, thereby causing the inner rail 94 to slip on the intermediate rail 95. In this case, the intermediate rail 95 cannot be simultaneously moved with the inner rail 94 out of the outer rail 96. Because the stop member 97 has a fixed end pivoted to the inner rail 94 by a pivot 98 and a downward protruding plate 971 extended from the free end thereof and stopped against a retaining block (not shown) of the outer rail 96, the stop member 97 tends to be forced to curve upwards upon inward movement of the intermediate rail 95. Frequently curving the stop member 97 may loosen the stop member 97. Furthermore, the spring 99 which is installed in the intermediate rail 95 to support the stop member 97, has only one end 991 stopped against a stop flange 942 of the intermediate rail 95, it tends to be forced out of position when moving the drawer in or out of the desk.
The present invention has been accomplished to provide a sliding track assembly for drawer, which eliminates the drawbacks of the aforesaid prior art designs. According to one aspect of the present invention, the sliding track assembly comprises an outer rail fixedly mounted inside a desk, an intermediate rail carried on a first sliding bearing and moved in and out of the outer rail, an inner rail carried on a second sliding bearing and moved with a drawer in and out of the intermediate rail, a stop member mounted in a sliding slot on the intermediate rail and forced by the spring on the intermediate rail to limit forward movement of the inner rail relative to the intermediate rail, a first sliding bearing coupled between the inner rail and the intermediate rail, a second sliding bearing coupled between the intermediate rail and the outer rail, and a locating plate fixedly fastened to the inner rail at one end to limit forward movement of the inner rail relative to the intermediate rail. According to another aspect of the present invention, the inner rail has a raised portion formed on a front side thereof to contact an upward side flange of the stop member when pulling the drawer out of the desk, keeping the intermediate rail to be moved with the inner rail and the drawer, so that the inner rail and the intermediate rail concomitantly bear the movement of the drawer during the first step. According to still another aspect of the present invention, the intermediate rail, the second sliding bearing, the stop member, the first sliding bearing, and the locating plate are moved in the same direction without causing an interference when pulling the inner rail with the drawer out of the intermediate rail or pushing the drawer back to the inside of the desk. According to still another aspect of the present invention, when pressing the free end of the locating plate, the inner rail is disengaged from a positioning block of the intermediate rail, and the inner rail can then be removed with the drawer from the intermediate rail. According to still another aspect of the present invention, the stop member has a supporting rib bridging the sliding slot of the intermediate rail to positively support the stop member on the intermediate rail against the stop portion of the retaining block of the outer rail. According to still another aspect of the present invention, the intermediate rail has integrated retaining flanges abutting two sides of a curved positioning portion of the spring to hold the spring in place.